The present invention relates generally to undesirable rattle that sometimes occurs in steering racks of vehicle steering systems, and more particularly to a test procedure for being able to determine a propensity for rack rattle in a vehicle from a lab test.
In conventional rack and pinion steering systems for vehicles, wear occurs in the rack and pinion system that results in increased clearance between components. Typically, the wear occurs at the interface of the rack with the pinion and in the system that preloads the rack to the pinion. The clearance resulting from the wear then results in rattles inside the steering rack that can be heard by the vehicle occupants, typically when they are driving over rough roads. The wear may actually occur early in a vehicle's life, costing a great deal to replace a steering rack or steering column, and possibly reducing a vehicle owner's satisfaction with the vehicle overall. Occasionally, depending on the design or initial settings, some racks and columns even rattle when new.
Since steering rack rattle is an audible event that can be heard by vehicle occupants, the rattle events can be binaurally recorded while driving a vehicle on rough roads and played back with high accuracy. But there is generally too much extraneous noise in these recordings to allow for objective analysis based solely on these recordings. Consequently, the typical steering rack rattle performance ratings are determined subjectively on random road test events, making repeatability very difficult. Moreover, since this is done on a vehicle level test, other components in the vehicle can make noise during the test that make it even more difficult to correctly determine the noise levels of the steering system separate from these other noises.